UPD78F9234MC-5A4-A Datasheet, PDF (82/419 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

CHAPTER 5 CLOCK GENERATORS
Figure 5-7. Examples of Incorrect Resonator Connection (2/2)
(e) Signals are fetched
VSS
X1
X2
5.4.3 External clock input circuit
This circuit supplies a clock from an external IC to the X1 pin.
If external clock input is selected by the option byte as the system clock source, the X2 pin can be used as an I/O
port pin.
For details of the option byte, refer to CHAPTER 18 OPTION BYTE. For details of I/O ports, refer to CHAPTER 4
PORT FUNCTIONS.
5.4.4 Prescaler
The prescaler divides the clock (fX) output by the system clock oscillator to generate a clock (fXP) to be supplied to
the peripheral hardware. It also divides the clock to peripheral hardware (fXP) to generate a clock to be supplied to the
CPU.
Remark The clock output by the oscillator selected by the option byte (high-speed internal oscillator,
crystal/ceramic oscillator, or external clock input circuit) is divided. For details of the option byte, refer to
CHAPTER 18 OPTION BYTE.
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User’s Manual U17446EJ5V0UD